1. Field
Example embodiments relate to semiconductor devices having a dielectric layer of a high dielectric constant and to methods of manufacturing semiconductor devices.
2. Description of the Related Art
As a result of semiconductor devices becoming more highly integrated, the area of a unit cell has been significantly reduced, and the operational voltage has been lowered, as well. Accordingly, a dielectric layer having a high dielectric constant (high-k) has been applied to semiconductor devices to enhance electrical storage performance and/or to suppress leakage current through the dielectric layer.
Generally, a high-k dielectric layer has a thin equivalent oxide thickness (i.e., a low thickness of SiO2 gate oxide would exhibit the same gate capacitance) and a high dielectric constant, so the high-k dielectric layer may improve the capacitance of a capacitor or a coupling ratio of a flash memory device, or the high-k dielectric layer may provide a proper threshold voltage of a metal gate structure.
For example, a hafnium oxide (HfO2) layer, a tantalum oxide (Ta2O5) layer, an aluminum oxide (Al2O3) layer and a zirconium oxide (ZrO2) layer have been used as the high-k dielectric layer of a capacitor (e.g., a metal-insulator-metal capacitor). These dielectric layers have a high dielectric constant, so these dielectric layers may improve dielectric characteristics of a device. As a design rule decreases, a dielectric layer having a very thin equivalent oxide thickness has also been utilized for a further scaling down. Further, these dielectric layers may be crystallized during a subsequent annealing process. When crystallization of a dielectric layer occurs, a threshold voltage of a gate may not be uniform along a channel length, and a leakage current that deteriorates the reliability of the semiconductor device may be generated.